Significant skin wounds, such as are caused by injury or surgery, frequently lead to scarring. Scarring in many instances results in a diminished sense of touch, loss of flexibility and loss of range of motion (where scars run across joints). Scarring also results in obvious cosmetic problems, particularly when on the face and hands. Skin wounds are also prone to infection, and even with conventional dressings, infections are fairly common. Burn victims are particularly susceptible to infections, and can be left with severe scarring when the wounds heal. There is a need for methods of treatment of skin injuries that minimize or eliminate scar formation.
Conventional wound dressings, such as are made from cotton gauze and various polymers, leave much to be desired, especially when a large area of skin must be dressed. The ability of the dressing to remain in place and protect the wound becomes progressively more compromised as the area of the wound increases, while at the same time the removal the dressing without injury to the underlying tissue becomes progressively more difficult. Wound dressings must stretch and flex to accommodate the movement of muscles and joints; this too gets more difficult as the dressing gets larger. In the case of facial dressings, it is desirable to minimize the visual impact of the dressing, and this of course rapidly becomes impossible as the size of the wound increases. Finally, conventional wound dressings require frequent changing, which is particularly costly in a hospital setting where the time value of professional staff, and the costs of disposing of medical waste, are significant. There is a need for improved wound dressings that do not have these disadvantages.
To address these needs, a number of products have been developed and marketed (Reviews: L. Borgognoni, Wound Repair and Regeneration (2002), 10:118-121; D. Leventhal et al., Arch Facial Plast Surg (2006), 8:362-368). Among the more successful are silicone gel sheets (“SGS”) and silicone gel ointments, and combinations thereof. The use of these silicone-based polymers and gels has been proven to reduce the appearance of scars when used consistently for sufficiently extended periods of time. (Chan, K Y, et al., Plast Reconstr Surg. (2005), 116:1013-1020; Signorini M, Clementonil M T., Aesthetic Plast Surg. (2007), 31:183-187; Chernoff W G, et al., Aesthetic Plast Surg. (2007) 31:495-500; Fonseca Capdevila E, et al., Piel (2007) (in press); Sepehrmanesh M., Kompendium Dermatologie (2006), 1:30-32; Murison M, James W., J Plast Reconstr Aesthet Surg. (2006), 59:437-439.)
It is impractical to use sheeting on large areas and near joints, and it cannot be used easily on the face and other areas where the contours or motility of the skin make it difficult to ensure adequate contact and coverage. Taping is often needed to secure the sheeting to the skin. Also, patients may be reluctant to use the sheeting on unclothed areas during the day, making compliance with treatment a concern. Finally, the sheets must be washed frequently to prevent complications such as rashes and infection.
Although the mechanism by which silicone sheets and polymers reduce the appearance of scars is not presently known, it has been hypothesized that the silicone provides a barrier function that somehow promotes the healing process. This may involve increased hydration, pH control, increased temperature, and control of oxygen tension. The presence of unspecified silicone compounds in the healing skin have been proposed to somehow limit scar formation. Commercial products formed from silicone-based polymers and specifically targeting wound healing and the treatment of existing scars are presently available. Specific examples of such commercial products include Neosporin Scar Solutions™ sheets, Cica-Care™ sheets, Mepiform™ scar dressings, and Dermatix™ silicone gel.
Silicone polymer gel compositions for wound treatment have been described (see for example U.S. Pat. No. 5,741,509). Although the silicone-based polymers are effective in reducing the appearance of scars, the known compositions must be applied to the scars for long periods of time in order to achieve noticeable results. In particular, the silicone-based polymer gels are typically worn on the scars for about 18 hours per day, every day, for several months. Significant discomfort may result from the long periods during which the silicone-based polymers must be worn on the scar. Also, the typical gel is a viscous material that leaves a relatively thick layer on the skin, which is at best imperfectly camouflaged with makeup. Although the layer of silicone can be rendered nearly invisible with suitably sophisticated cosmetic materials and methods, few patients have the time and resources to use these methods or to employ a professional cosmetologist. The resulting impairment of physical appearance can discourage patient compliance with the rigorous and unusually lengthy treatment protocol. There is a need for an effective silicone polymer composition that is more comfortable, less visible, and more easily rendered inconspicuous by ordinary cosmetics.